Recently there has been increased interest into molecular glasses that can be coated into amorphous films for applications such as photoresist or molecular optoelectronic devices, including light-emitting diodes, field-effect transistors, and solar cells, as well as in advanced materials for xerography, two-photo absorption, luminescent devices, and photorefraction. One technique that is used in the art is a reverse of the principles of crystal engineering to devise molecules that resist crystallization. Examples of this technique are described in the publications by Eric Gagnon et al: “Triarylamines Designed to Form Molecular Glasses. Derivatives of Tris (p-terphenyl-4-yl) amine with multiple Contiguous Phenyl Substituents.” Organic Letters 201, Vol. 12, No. 3, p 404-407.
These molecular glasses produced via reverse crystallization engineering are defined as “amorphous materials in the state of thermodynamic non-equilibrium, and hence, they tend to undergo structural relaxation, exhibiting well-defined glass temperature (Tg's). However they also tend to crystallize on heating above their Tg's, frequently exhibiting polymorphism” (Hari Singh Nalwa, Advanced Functional Molecules and Polymers, Volume 3, CRC Press, 2001—Technology & Engineering; Yashuhiko Shirota and Hiroshi Kageyama, Chem. Rev. 2007, 107, 953-1010). With time, equilibrium will lead to crystallization of these non-equilibrium molecular glasses. Therefore crystallization is still a problem to be solved. When these non-equilibrium molecular glasses crystallize, the performance of a device comprising the non-equilibrium molecular glasses is degraded, limiting device longevity. An additional problem with current small molecule organic light emitting diode (OLED) materials is their solubility; either solubility is limited or requires non-green solvents.
A further issue with molecular glass usage involves fluorescent emitters, particularly blue fluorescent emitters aggregation quenching. To suppress fluorescent quenching, blue fluorescent dyes have been doped in a host matrix. The blending system may intrinsically suffer from the limitation of efficiency and stability, aggregation of dopants and potential phase separation (M. Zhu and C Yang, Chem. Soc. Rev., 2013, 42, 4963). Another method used for blue fluorescent organic light emitting diodes (OLEDs) is nondoped blue fluorescent emitters. Still charge injection and transportation remain a problem.
Molaire in U.S. Pat. No. 4,499,165 disclosed nonpolymeric amorphous mixtures of compounds which are useful as a binder in optical recording layers. These mixtures were further used in nonpolymeric amorphous composition and developing processes (U.S. Pat. No. 5,176,977). Monomeric glass mixtures incorporating tetracarbonylbisimide groups were disclosed in U.S. Pat. No. 7,776,500. In U.S. Pat. No. 7,629,097 these mixtures found use in encapsulated toner compositions incorporating organic monomeric glasses. The entire disclosure of each of these United States patents is hereby incorporated by reference into this specification. In U.S. patent application Ser. Nos. 14/467,143 and 14/578,482 by Molaire, charge transporting molecular glass mixtures, bipolar charge-transporting molecular glass mixtures, electroluminescent (bipolar) molecular glass mixtures, and crosslinkable molecular glass mixtures are disclosed. In the molecular glass mixtures of those disclosures the mixture comprises at least two different components joining one multivalent organic nucleus with at least two organic nuclei wherein at least one of the multivalent organic nucleus and the organic nuclei is multicyclic, the linking group being an ester, urethane, amide or imide group.
Most luminescent organic molecules are pi-conjugated compounds, i.e., materials in which single and double or single and triple bonds alternate throughout the molecule or polymer backbone. For fine line photoresist applications, it is important to minimize linking groups that contribute to light absorption above 250 nm.
There is a need for non-crystallizable molecular glasses that are fully pi-conjugated. There is a need for non-crystallizable molecular glasses for resist applications. There is a need for charge-transporting molecular glasses, luminescent molecular glasses, and combinations thereof that are truly non-crystallizable. There is further need for charge-transporting molecular glasses, luminescent molecular glasses, and combinations thereof with controllable thermal properties, independent of the structure of the charge transport moiety. There are specific needs for charge-transporting molecular glasses, luminescent molecular glasses, and combinations thereof that are relatively inexpensive to manufacture. There is a need to develop host matrix that will prevent phase separation of the guest emitter materials. There is also a need to develop luminescent emitters that will not aggregate in the first place. There is a need for charge-transporting molecular glasses, luminescent molecular glasses, and combinations thereof that are truly non-crystallizable. There is further need for charge-transporting molecular glasses, luminescent molecular glasses, and combinations thereof with large entropy of mixing to allow for complete compatibility of guest emitter materials. There is a further need for charge-transporting molecular glasses, luminescent molecular glasses, and combinations thereof where the polarity of transport can be easily modulated. There is still need for charge-transporting molecular glasses, luminescent molecular glasses, and the like that are bipolar and truly non-crystallizable.
The present invention provides solutions for the above problems.
It is an object of this invention to provide non-crystallizable molecular glasses that are fully pi-conjugated. It is an object of this invention to provide non-crystallizable molecular glasses for resist applications. It is and object of this invention to provide charge-transporting molecular glass mixtures, luminescent molecular glass mixtures, and combinations thereof with the many of the advantages illustrated herein. It is also an object of this invention to provide charge-transporting molecular glass mixtures, luminescent molecular glass mixtures, and combinations thereof that can be purified by simple and economic techniques. In another object of this invention there are provided charge-transporting molecular glass mixtures, luminescent molecular glass mixtures, and combinations thereof that can be easily dissolved in simple organic solvents. It is yet another object of this invention to provide charge-transporting molecular glass mixtures, luminescent molecular glass mixtures, and combinations thereof volatile and stable enough for vacuum deposition coatings. It is another object of this invention to provide charge-transporting molecular glass mixtures, luminescent molecular glass mixtures, and combinations thereof with uniform vapor pressure for vacuum deposition coatings without components fractionation. It is yet a further object of this invention to provide charge-transporting molecular glass mixtures, luminescent molecular glass mixtures, and combinations thereof with both sufficient electron-transporting and hole-transporting properties to support monolayer or simple device configuration.